Various types of digital ignition systems have been proposed. The present system is a further development of the type of ignition system described in U.S. Pat. No. 3,908,616 Sasayama. This patent discloses a system in which a switch closes to permit current to flow through the primary of an ignition coil when a counter has reached a certain count state. The particular count state of the counter depends on the type of engine with which the system is used. A decoding stage is provided to decode the specific count state. Such decoding stages customarily include a plurality of logic gates. When such a system is to be matched to various types of internal combustion engines using different ignition coils and requiring different closed time periods for the switch to store the appropriate quantity of electromagnetic energy therein, in short, have different dwell times, to use the terminology customary with breaker-type systems, it is necessary to change the arrangement of the gates in the decoding system in order to match the dwell period or dwell time commanded by the system to the particular engine, while retaining the accuracy of setting of the ignition instant with respect to a predetermined angular crankshaft position. Changing the wiring or connection of gates in a decoding stage is labor-intensive and hence expensive.